1. Field of the Invention
The present invention relates to an image display apparatus such as an electron beam emitting device or a display device and its application and a method of manufacturing the image display apparatus.
2. Related Background Art
Conventionally, two types of electron-emitting devices, that is, a thermionic cathode electron emitting device and a cold cathode electron emitting device, are known as the electron-emitting device. Of these devices, as the cold cathode electron-emitting device, for example, a surface conduction type electron emitting device, a field emission type (hereinafter referred to as an FE type), a metal/insulating-layer/metal type (hereinafter referred to as an MIM type), and the like are known.
As the surface conduction type electron emitting device, the example described in M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965) and another example described later are known.
The surface conduction type electron emitting device is realized by utilizing the phenomenon that electrons are emitted out of a small area thin film formed on a substrate when a current is made to flow in parallel with respect to the film surface. As the surface conduction type electron emitting device, in addition to the device using an SnO2 thin film by above-mentioned Elinson et al., a device using an Au thin film (G. Dittmer: “Thin Solid Films”, 9, 317 (1972)), a device using an In2O3/SnO2 thin film (M. Hartwell and C. G. Fonstad: “IEEE Trans. ED Conf.”, 519 (1975)), a device using a carbon thin film (H. Araki et al.: Vacuum, Vol. 26, No. 1, 22 (1983)), and the like, have been reported.
As a typical example of a device structure of these surface conduction type electron emitting devices, a plan view of the above device by M. Hartwell and C. G. Fonstad is shown in FIG. 19. In this drawing, reference numeral 3001 denotes a substrate and 3004 denotes an electroconductive thin film which is made of metal oxide and formed by sputtering. The electroconductive thin film 3004 is formed into an H-shaped plane form as shown in the drawing. An energization operation and called an energization forming which is described later is performed for the electroconductive thin film 3004 to form an electron emitting region 3005. In the drawing, an interval L is set to be 0.5 mm to 1 mm and W is set to be 0.1 mm. Note that, for the convenience of illustrating, the electron emitting region 3005 is shown with a rectangular form in the center of the electroconductive film 3004. However, this is a schematic view and does not precisely show the position and the form of the actual electron emitting region.
In the above surface conduction type electron emitting device such as the device by M. Hartwell and C. G. Fonstad, generally, before electron emitting, an energization operation which is called an energization forming is performed for the electroconductive thin film 3004 to form the electron emitting region 3005. That is, in the energization forming, a constant direct current voltage or a direct current voltage increased at an extremely slow rate such as about 1 V/minute is applied to both ends of the electroconductive thin film 3004 to make the energization. Thus, the electroconductive thin film 3004 is locally broken, deformed, or deteriorated to form the electron emitting region 3005 with an electrically high resistance state. Note that, a fissure is generated in a portion of the electroconductive thin film 3004 which is locally broken, deformed, or deteriorated. When a suitable voltage is applied to the electroconductive thin film 3004 after the energization forming, the electrons are emitted at the vicinity of the fissure.
Also, as the FE type, the examples disclosed in W. P. Dyke & W. W. Dolan, “Field Emission”, Advance in Electron Physics, 8, 89 (1956), C. A. Spindt, “Physical Properties of Thin-film Field Emission Cathodes with Molybdenum Cones”, J. Appl. Phys., 47, 5248 (1976), and the like are known.
As a typical example of a device structure of the FE type, a cross sectional view of the above device by C. A. Spindt et al. is shown in FIG. 20. In the drawing, reference numeral 3010 denotes a substrate, 3011 denotes an emitter wiring made of an electroconductive material, 3012 denotes an emitter cone, 3013 denotes an insulating layer, and 3014 denotes a gate electrode. This device causes, by applying a suitable voltage between the emitter cone 3012 and the gate electrode 3014, the field emission from the end portions of the emitter cone 3012.
Also, as another device structure of the FE type, there is an example in that an emitter and a gate electrode are located on a substrate substantially parallel with a surface of the substrate without using a lamination structure as shown in FIG. 20.
As the MIM type, the examples described in C. A. Mead, “Operation of Tunnel-Emission Devices”, J. Appl. Phys., 32, 646 (1961), and the like are known. A typical example of a device structure of the MIM type is shown in FIG. 21. This drawing is a cross sectional view. In the drawing, reference numeral 3020 denotes a substrate, 3021 denotes a lower electrode made of metal, 3022 denotes a thin insulating layer having a thickness of about 100 angstroms, and 3023 denotes an upper electrode which has a thickness of about 80 to 300 angstroms and made of metal. In the MIM type, a suitable voltage is applied between the upper electrode 3023 and the lower electrode 3021, and thus the electron emitting from the surface of the upper electrode 3023 is produced.
In the above cold cathode electron-emitting device, since the electron-emitting can be obtained at lower temperature than in the thermionic cathode electron-emitting device, a heater is not required. Therefore, the structure of the cold cathode electron-emitting device is simpler than that of the thermionic cathode electron-emitting device, and thus a minute device can be manufactured. Even when a large number of devices are arranged in a high density on the substrate, it prevents the problem such as thermal melting of the substrate to cause. Also, while a response speed of the thermionic cathode electron-emitting device is low because it is operated by heating of the heater, there is an advantage that a response speed is high in the case of the cold cathode electron-emitting device.
Therefore, studies for applying the cold cathode electron-emitting device have been greatly performed. Of the cold cathode electron-emitting devices, for example, the surface conduction type emitting device, in particular, has a simple structure and is easily manufactured. Thus, there is an advantage that a large number of devices can be formed over a large area. As disclosed in, for example, Japanese Patent Application Laid-Open NO. 64-31332 by the present applicant, a method of arranging a large number of devices and driving them has been studied.
As an application of the surface conduction type emitting device, an image display apparatus, an image display apparatus used in an image recording apparatus, a charged beam source, and the like have been studied.
In particular, as an application to the image display apparatus, as disclosed in, for example, U.S. Pat. No. 5,066,883 and Japanese Patent Application Laid-Open Nos. 2-257551 and 4-28137 by the present applicant, an image display apparatus using a combination of the surface conduction type emitting device and a phosphor for emitting light by an irradiation of an electron beam has been studied. With respect to the image display apparatus using a combination of the surface conduction type electron emitting device and the phosphor, a characteristic superior to that of a conventional image display apparatus with another system is expected. For example, when it is compared with a liquid crystal display device which comes to be widely used in recent years, there are advantages in that a backlight unit is not required because it is a self light emitting type, and in that a viewing angle is wide.
A method of arranging a large number of FE type devices and driving them is disclosed in, for example, U.S. Pat. No. 4,904,895 by the present applicant. Also, as an example that the FE type is applied to the image display apparatus, for example, a flat panel display reported by R. Meyer et al. is known (R. Meyer: “Recent Development on Micro-tips Display at LETI”, Tech. Digest of 4th Int. Vacuum Microelectronics Conf., Nagahama, pp. 6-9 (1991)).
An example that a large number of MIM type devices to be arranged are applied to the image display apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-55738 by the present applicant.
Of the image display apparatuses using the above electron-emitting device, the flat panel display which is thin in a depth dimension is space-saving and lightweight. Thus, this is noted as a display which replaces a cathode-ray tube type display.
FIG. 22 is a perspective view of a portion of a display panel portion composing the flat panel display using a cold cathode electron-emitting device. In FIG. 22, in order to show an inner structure, a portion of the panel is cut.
In the drawing, reference numeral 3115 denotes a rear plate, 3116 denotes a side wall, and 3117 denotes a face plate. An envelope (airtight container) for keeping the inner portion of the display panel in a vacuum state is formed by the rear plate 3115, the side wall 3116, and the face plate 3117.
A substrate 3111 is fixed to the rear plate 3115. An N×M of electron-emitting devices 3112 are formed on the substrate 3111. Symbols N and M are positive integers which are equal to or larger than two and suitably set in accordance with the number of display pixels to be required. As shown in FIG. 22, the N×M of electron-emitting devices 3112 are wired using M-row-directional wirings 3113 and N-column-directional wirings 3114. A portion composed of the substrate 3111, the electron-emitting devices 3112, the row-directional wirings 3113, and the column-directional wirings 3114 is called a multi-electron beam source. In portions where the row-directional wirings 3113 and the column-directional wirings 3114 are at least intersected, insulating layers (not shown) are formed between both the wirings to keep the electrical insulation.
A fluorescent film 3118 made of phosphors is formed on an undersurface of the face plate 3117. The phosphors with three primary colors (red (R), green (G), and blue (B)) (not shown) are applied to the fluorescent film 3118. Also, black color members (not shown) are provided between the phosphors with the above respective colors, which composes the fluorescent film 3118. Further, a metalback 3119 made of Al or the like is formed on a surface of the fluorescent film 3118, which is in the side of the rear plate 3115.
Reference symbols Dx1 to Dxm, Dy1 to Dyn, and Hv denote electrical connecting terminals with an airtight structure, which are provided to electrically connect the display panel to electrical circuits (not shown). The terminals Dx1 to Dxm are electrically connected to the row-directional wirings 3113 of the multi-electron beam source, the terminals Dy1 to Dyn are electrically connected to the column-directional wirings 3114 of the multi-electron beam source, and the terminal Hv is electrically connected to the metalback 3119.
The inner portion of the above airtight container is kept in a vacuum of about 10−6 Torr. As the display area of the image display apparatus is increased, means for preventing deformation or break of the rear plate 3115 and the face plate 3117 due to an atmospheric pressure difference between the inner portion of the airtight container and its external is required. In the case of a method for thickening the rear plate 3115 and the face plate 3117, the weight of the image display apparatus is increased, and the distortion or the parallax of an image is caused when it is viewed from an oblique direction. On the other hand, in FIG. 22, structure supports (which are called spacers or ribs) 3120 which are made from a relatively thin glass plate and keep an atmospheric pressure, are provided. Thus, an interval between the substrate 3111, on which the multi-electron beam source is formed, and the face plate 3117, on which the fluorescent film 3118 is formed, is kept by generally submillimeters to several millimeters. As described above, the inner portion of the airtight container is kept in a high vacuum.
According to the above described image display apparatus using the display panel, when voltages are applied to the respective cold cathode electron-emitting devices 3112 through the container external terminals Dx1 to Dxm and Dy1 to Dyn, electrons are emitted from the respective cold cathode electron-emitting devices 3112. Simultaneously, a high voltage of several hundreds volts to several kilovolts is applied to the metalback 3119 through the container external terminal Hv to accelerate the emitted electrons. Thus, the electrons are collided with the inner surface of the face plate 3117. As a result, the phosphors with respective colors, composing the fluorescent film 3118, are excited to emit lights, and then the image is displayed.